Electrical Contracting News (ECN) July 2017 - Page 37

FIRE DETECTION & SAFETY in which the output meets the minimum illumination requirement of 0.4 lumens/m 2 (lux) on a perpendicular surface. To avoid having to install an unacceptably large number of beacons, manufacturers are typically designing to meet smoke detector spacings. The result is that W class devices are assessed in terms of the dimensions of the cube of light they cover and C devices are assessed as the diameter of a cylinder of light. The coverage of an O class device is a cuboid of light, defined by the manufacturer as independent of the EN54-23 height/ placement requirements. A further important consideration is that if the risk assessment does not specify a VAD for a particular area, it will still be acceptable to install a non- compliant beacon as a supplementary indicator to a sounder. SPECIAL FEATURE ‘The development of EN54-23 required a fundamental change in visible alarm technology.’ Red or white flash? The fire industry has traditionally used a red flash to denote an alarm condition. This presented a challenge under EN54- 23, as the light intensity drops as it is filtered through a red lens, requiring more power to achieve the required coverage. This loss can be as much as 80 per cent. Installers and specifiers need to be aware of this when selecting a VAD. If an existing installation has VADs with red flash then the colour of the flash has to remain the same on any replacements or extensions to the system. Specifying When selecting a beacon, room coverage, flash colour and current consumption are the key measures. The milliamp per metre specification of a product offers a good guide to selecting the most efficient VAD possible. The introduction of EN54-23 has led to growth in the use of VADs and this is set to continue. They offer the reassurance of a visual indication to a fire alarm and help to mitigate the risk to the building occupants. Fully automated and highly reliable, used as part of a comprehensive fire detection system, VADs remove any human error associated with systems that rely on human interaction or the requirement to ensure that portable tactile devices are working and that the batteries are charged. The standard enforces a specific illumination level, ensuring that any visual alarm is meaningful and inclusive to all. The introduction of EN54-23 has led to growth in the use of VADs. METAL NAIL CLIPS AD - ECN_Layout 1 20/06/2017 11:29 Page 1 Meets the requirements of BS7671 3rd Amendment 7th Edition To find out more contact us: on our FREEPHONE number 0 8 0 8 1 6 4 2 2 0 4 distribution@hellermanntyton.co.uk